A friend of mine was going to be interviewed along with a climate denier. I put together these talking points to help him. You may find them useful as well.

These points focus on some of the deniers more recent claims. You will find lots of sites debunking other deniers claims in on the Links page.

I've put these points in the form of potential questions you may be asked. I'll provide the quick answer and will also provide backup information for your review. I've bolded and underlined "sound bites".

1. It snowed a lot in the U.S. in February and some have said this disproves Global Warming. What do you think?

Of course you know there is a difference between weather -- what happens day to day -- and climate -- the long-term average. So, any specific weather event such as a big snowfall or cold spell says nothing about global warming. But you can say that the large amount of snow is consistent with predictions that climate change will lead to more large precipitation events. In fact, the number of high precipitation events has been increasing over the last few decades. Also, while it seems a little counter-intuitive, it snows more in warm winters than in cold winters because warm air holds more moisture than cold air. It is so cold in most parts of Antarctica that it almost never snows and those parts are considered deserts!

While climate change predictions say that temperatures will get warmer on average over time, but certainly no scientist thinks or has said that it won't snow anymore! And anyone who suggests otherwise is being disingenuous at best.

2. It was really cold in January in the U.S. Doesn't that disprove global warming?

Again, there is a difference between weather -- what happens day to day -- and climate -- the long-term average. While it was cold in the U.S. and Asia, the rest of the world -- and especially the Arctic -- was quite warm. In fact, according to NASA, this last January (2010) was the warmest January since they began measuring global temperature with satellites 32 years ago. Climate change says that the long-term average temperature will increase and what we have seen is thatrecord high temperatures now occur about twice as often as record low temperatures. Record lows still occur, just not as often as record high temperatures.

And while specific weather events don't tell us anything about climate change, long-term averages do. And we know that the last decade (2000-2009) was the warmest decade since we started measuring temperature, and the decade before that is the second warmest. This is clearly in line with CC predictions.

3. The "Climategate" emails talked about "tricks" and hiding data that didn't show warming. Doesn't this show that climate scientists are "cooking the books"?

While the stolen emails show how some scientists communicate in private, nothing in the emails showed that scientists fudged data. One scientist used the word "trick", as in "trick of the trade" or, in other words, a quick way to handle data accurately. The scientists may have tried to influence journal editors about what to publish, but that, of course, is what peer review is about. The bottom line is that the emails do nothing to contradict the scientific consensus on climate change.

4. Thousands of scientists have signed a petition that says climate change isn't happening, isn't serious and/or isn't caused by humans. How can you disregard these scientists?

You can get a survey to show almost anything, including that aliens have abducted people for science experiments. The purported climate change surveys did not check for the qualifications of who signed them and they contained very few, if any, climate scientists among them. 97% of climate scientists agree that climate change is happening and is man-made.

If your child has cancer, you're going to take him or her to a pediatric oncologist, not a dentist or an ophthalmologist. And if the oncologist says your child needs treatment, you're not going to withhold it because the doctor is only 95% certain of the diagnosis or the fact that the doctor will earn money from providing the treatment. The climate scientists are the experts that are telling us we need to take action now. To withhold treatment is to endanger the future of our children.

It has not been cooling since 1998. 1998 was a very warm year because of a very strong El Nino that year. So, while 1998 was a high data point in a rising (but noisy) trend, it does not imply that the temperature trend is going down now. In fact, according to NASA, 2005 was the warmest year on record, not 1998. And, because an El Nino condition exists now, it is expected that 2010 will be the warmest year ever. In addition, the last decade (2000-2009) was the warmest since temperature measurements began, so it is rather absurd to say that it has been cooling since 1998.

6. Most scientists in the 1970's said there would be global cooling. Why should we believe them now?

It's not true. While a few scientists talked about global cooling in the 1970's (which occurred in the 1950's and 1960's due to aerosol cooling due to air pollution that outweighed warming due to CO2 growth), the majority of climate scientists back then that predicted a temperature change, predicted their would be global warming, not cooling.

7. There has been a lot of talk in the press recently about mistakes in the UN IPCC reports. Doesn't that mean that climate change may not be real?

No. The errors that were identified (such as how soon the Himalayan glaciers will melt), did not show that there were any errors in the overall science of climate change. The fact that CO2 in the atmosphere warms the earth is not really debatable… you can measure it in the laboratory! However, many climate scientists, including IPCC climate scientists, believe the IPCC report is a consensus driven "best case" analysis of what will happen if we continue on the emissions path we are on and that the actual impacts from climate change could be far worse than the IPCC predicted. The summer Arctic sea ice is melting much faster than the IPCC predicted. Sea level rise is now expected to be much higher this century than the IPCC predicted (4 to 6 feet vs. 1 to 2 feet). Some scientists think there is a 50% chance that the global average temperature could increase by 5C (9F!) this century under business-as-usual emissions. The message is clear that we must act now to dramatically reduce our greenhouse gas emissions.

8. Scientists just withdrew a peer-reviewed paper on sea level rise. Doesn't that mean that scientists don't know whats going on and we now don't need to worry about sea level rise?

No! The paper in question, by Mark Sidall, claimed that sea level rise could not be more than 32 inches this century. But based on corrections from other scientists (part of the scientific process!), Mark withdrew his paper because he now agrees that sea level rise could be much higher this century!